1) Field of the Invention
The present invention relates to a level conversion circuit for converting binary logic signals having a certain amplitude into binary logic signals having another amplitude.
2) Description of the Related Art
Generally, since digital circuit elements have a general purpose, a so-called standard logic is predetermined for the digital circuit elements. As the standard logic, there are emitter-coupled logic (ECL) having an amplitude of about 1 V, transistor-transistor logic (TTL) having an amplitude of about 1 V, CMOS logic having an amplitude of about 2 V, and the like. Therefore, a logic level conversion is required in signal transmission between different standard logic levels, and a level conversion circuit is used for that purpose.
In a prior art level conversion circuit, binary logic input signals having an amplitude are received by two input transistors, and the potentials of the binary logic input signals are shifted down by diodes. Then, the level-shifted binary logic signals are supplied to a differential amplifier, thereby obtaining binary logic output signals having another amplitude, which will be explained later in detail.
In the prior art, however, the differential amplifier cannot operate at high speed unless a large current is supplied thereto. Therefore, the prior art level conversion circuit having high speed of operation also has a large power consumption.
Also, in the prior art, various levels of binary logic output signals cannot be generated.